Voglio segnalare come risolvere il problema indicato nel titolo, come dai commenti del blog che ho linkato:
1) Create the project in XCODE.
2) Setup subversion in XCODE and select the subversion repository for this project.
3) Use Xcode SCM > Repository and click on the IMPORT icon. This will move the local copy to the subversion repository.
5) Now delete your local copy (or move it to another location just in case).
6) Finally CHECKOUT the project from subversion (this will create the subversion .svn folders, …).